The Effects of Ion Beam Mixing on Rapid Thermal Annealed Ohmic Contacts to N-GaAs

Ni/Ge/Au and Ni/Ge/Pd contacts have been made on 1018 cm-3 n-type GaAs. The contacts were subjected to ion beam mixing through the metallization using 70–130 keV Se+ ions and subsequently subjected to rapid thermal annealing (RTA). These are compared with unimplanted contacts produced by RTA techniques on the same substrate. The specific contact resistance,juc, has been measured for the two systems. In addition, the contacts have been studied using Auger depth profiling and SEM studies have been used to determine surface morphology. Values of juc ∼ 10−6 −10−7 ohm-cm2 have been measured. It is observed that ion beam mixing or the addition of a Ti overlayer (to the Ni/Ge/Au) improves the contact morphology.